This notable Irish surname is an Anglicized form of the Old Gaelic "O'Niallain", descendant(s) of Niallain, itself a diminutive of the male given name Niall, from the Gaelic "niadh", champion. The legendary Niall of the Nine Hostages, High King of Ireland (377 - 405), is the earliest known bearer of the forename, and from him descend the great O'Neills, a branch of the ancient royal family of Tara. The O'Niallain sept belonged to the ancient territory of Tuathmhumhan (Thomond), comprising most of Co. Clare with adjacent parts of Counties Limerick and Tipperary. Written in modern Irish as "O'Neilan", this family were the original owners of Ballyally Castle near Ennis in Co. Clare, which was also the family seat. From here the O'Neilans spread into Connacht, and three of the name are listed as persons of importance in the "Composition Book of Connacht", dated 1585. Other Anglicized forms of the name include: Neilan, Neylan(e), Nyland, Nilan, Niland, Nyland and Nilon. On December 17th 1838, Thomas, son of Daniel Nealon and Anne Sexton, was christened at Kilmaley, Co. Clare. The first recorded spelling of the family name is shown to be that of O'Niallain, a tanist abbot, which was dated 1093, in "Ecclesiastical Records of Clonmacnois, Co. Offaly, during the reign of High Kings of Ireland "with opposition", 1022 - 1166. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.